1.2. Three-Phase to Single-Phase (3f-1f) Cycloconverter:
There are two kinds of three-phase to single-phase (3f-1f) cycloconverters: 3f-1f half-wave cycloconverter (Fig. 4) and 3f-1f bridge cycloconverter (Fig. 5). Like the 1f-1f case, the 3f-1f cycloconverter applies rectified voltage to the load. Both positive and negative converters can generate voltages at either polarity, but the positive converter can only supply positive current and the negative converter can only supply negative current. Thus, the cycloconverter can operate in four quadrants: (+v, +i) and (-v, -i) rectification modes and (+v, -i) and (-v, +i) inversion modes. The modulation of the output voltage and the fundamental output voltage are shown in Fig. 6. Note that a is sinusoidally modulated over the cycle to generate a harmonically optimum output voltage.